With time travel debugging, data breakpoints become even more useful, because you can backtrack to the root cause once you've recorded the fault (rather than ne

With time travel debugging, data breakpoints become even more useful, because you can backtrack to the root cause once you've recorded the fault (rather than needing to run forwards and hope to replicate a corruption at the same location as last time). The GHCi Debugger (https://downloads.haskell.org/~ghc/7.8.3/docs/html/users_guide/ghci-debugger.html https://downloads.haskell.org/~ghc/7.8.3/docs/html/users_gui...) mentioned in another comment (https://news.ycombinator.com/item?id=31911462 https://news.ycombinator.com/item?id=31911462) can time travel but I don't see anything like a data breakpoint. I'm not quite sure what a meaningful functional equivalent would be given, semantically, no state is actually mutable in Haskell - but "where did this value come from?" still ought to be useful.